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Dithiocarbamate prodrugs activated by prostate specific antigen to target prostate cancer.

ABSTRACT: Disulfiram in conjunction with copper has been shown to be a potent anticancer agent. However, disulfiram's therapeutic potential in prostate cancer is hindered by off-target effects due to its reactive and nucleophilic thiol-containing component, diethyldithiocarbamate (DTC). To minimize undesirable reactivity, we have strategically blocked the thiol moiety in DTC with a cleavable p-aminobenzyl (pAB) group linked to peptide substrates recognized by prostate specific antigen (PSA). Here we report the synthesis and evaluation in cancer cell models of two PSA-activatable prodrugs: HPD (Ac-HSSKLQL-pAB-DTC and RPD (RSSYYSL-pAB-DTC). In vitro exposure to PSA was found to trigger activation of HPD and RPD to release diethyldithiocarbamate, and both prodrugs were found to induce toxicity in prostate cancer cells, with HPD showing the most promising selectivity. With copper supplementation, the IC₅₀ of HPD was 1.4 µM in PSA-expressing LNCaP cells, and 11 µM in PC3 cells that do not express PSA. These studies demonstrate the utility of using peptide recognition handles to direct the activity of dithiocarbamate prodrugs for selective cytotoxicity of cancer cells.

SUBMITTER: Bakthavatsalam S

PROVIDER: S-EPMC8330515 | biostudies-literature |

REPOSITORIES: biostudies-literature

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Project description:PURPOSE:To examine whether age-related reference ranges for "normal" prostate-specific antigen (PSA) change (determined in men without prostate cancer) can be used to identify men at high risk of having prostate cancer. METHODS:Subjects were men aged 50-69 years with PSA < 10 ng/mL from the UK-based Prostate Testing for cancer and Treatment (ProtecT) study. Men with prostate cancer were categorized as high or low risk of progression (Low risk: Gleason score ≤ 6 and stage T1-T2a; High risk: Gleason score 7-10 or stage T2C). Men without prostate cancer were those with no histological confirmation of prostate cancer. Previously developed longitudinal reference ranges for normal age-related PSA change were used to calculate an age-specific PSA threshold. We compared the ability of our age-specific PSA threshold to discriminate between high- and no/low-risk prostate cancer with that of two existing thresholds: (i) threshold of PSA = 3 ng/ml for all ages; (ii) National Institute of Clinical Excellence (NICE) guidelines dependent on age-group thresholds (age 50-59: PSA = 3 ng/mL; age 60-70: PSA = 4 ng/mL; age ≥ 70: PSA = 5 ng/mL). RESULTS:We included 823 men with high-risk prostate cancer and 80,721 men with no/low-risk prostate cancer. A threshold of PSA = 3 ng/ml for all ages identified more high-risk prostate cancers, recommending biopsy in 9.8% of men, of which 10.3% (n = 823) had high-risk prostate cancer. Using the NICE guidelines as the threshold for biopsy, 6.9% men were recommended for biopsy, of which 11.9% (n = 668) had high-risk prostate cancer. Using the new age-specific threshold for biopsy, 2.3% men were recommended for biopsy, of which 15.2% (n = 290) had high-risk prostate cancer. The age-specific threshold identified fewer high-risk prostate cancers, but fewer men received unnecessary biopsy. CONCLUSION:There is no benefit to using reference ranges for "normal" PSA that change with age nor the age-specific thresholds suggested by the NICE guidelines. While the age-varying thresholds are more discriminatory, too many high-risk cancers are missed.

Project description:BackgroundMost men will develop prostatic abnormalities, such as benign prostatic hyperplasia (BPH) or prostate cancer, as they age. Prostate-specific antigen (PSA) is a serine protease that is secreted at high levels by the normal and diseased prostate. Therapies that are activated by PSA may prove effective in treating prostatic malignancies.MethodsWe modified proaerolysin (PA), the inactive precursor of a bacterial cytolytic pore-forming protein, to produce a PSA-activated protoxin (PRX302). The viability of the prostate adenocarcinoma cell lines LNCaP, PC-3, CWR22H, and DU145 and the bladder cancer cell line TSU after treatment with PA or PRX302 in the presence or absence of purified PSA was assayed. Mice carrying xenograft tumors derived from LNCaP, CWR22H, or TSU cells were treated with intratumoral injection of PA or PRX302, and tumor size was monitored. To test the safety of PRX302, we administered it into the PSA-secreting prostate glands of cynomolgus monkeys. All statistical tests were two-sided.ResultsNative PA was highly toxic in vitro but had no tumor-specific effects in vitro or in vivo. Picomolar concentrations of PRX302 led to PSA-dependent decreases in cell viability in vitro (PRX302 versus PRX302 + PSA: DU145 cells, mean viability = 78.7% versus mean = 1.6%, difference = 77.1%, 95% confidence interval [CI] = 70.6% to 86.1%; P<.001; TSU cells, mean = 100.2% versus mean = 1.4%, difference = 98.8%, 95% CI = 96.4% to 104.0%; P<.001). Single intratumoral injections of PRX302 produced substantial and often complete regression of PSA-secreting human prostate cancer xenografts (5 microg dose, complete regression in 6 of 26 mice bearing LNCap or CWR22H xenografts [23%]; 10 microg dose, complete regression in 10 of 26 mice [38.5%]) but not PSA-null bladder cancer xenografts. The prostates of cynomolgus monkeys injected with a single dose of PRX302 displayed extensive but organ-confined damage, with no toxicity to neighboring organs or general morbidity.ConclusionsOur observations demonstrate the potential safe and effective intraprostatic application of this engineered protoxin.

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Dithiocarbamate prodrugs activated by prostate specific antigen to target prostate cancer.

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